The present invention relates to a spring-drive mechanism for electric switches which includes a drive shaft, a switch-on spring which can be put under tension by the drive shaft and which surrounds (coaxially encompasses) this drive shaft, and a hollow shaft situated co-axially around the drive shaft which supports at least one cam disc for operating the contacts of the switches. The mechanism is also one in which one end of the switch-on spring is fixedly connected to the drive shaft and the other end is fixedly connected to the hollow shaft, and includes structure which causes serial rotation of the hollow shaft over a certain angle as a result of influence of the energy stored in the tensioned switch-on spring and thereby causing operation of the switch contacts.
Such a switch-on mechanism is known from the German Auslegeschrift No. 1,690,038.
With known drive mechanisms the helical spring is put under tension by means of an electric motor via a ratchet with pawl, the release movement of the helical spring being opposed by a locking disc with relating locking pawl. By releasing the energy stored in the helical spring, the rotating movement of the helical spring is transmitted to a lever system by means of a cam disc and via the switch shaft on which this spring is wound, such that the rotating movement is converted into a reciprocating movement by which ultimately the movable contacts are operated. By using a lever system, however, the disadvantages of such a system itself are introduced. These disadvantages are for instance the deformation of the lever system resulting from the bending of the bars under the influence of the forces working on them, whilst the mass of the entire lever system influences the acceleration and the declaration of the entire mechanism. Also the various pivots of the lever system form an equal number of points of friction in which a certain amount of energy is lost.
An object of the present invention is to provide a spring drive mechanism of the type mentioned above by which these disadvantages are eliminated by eliminating the lever system, i.e., by applying a more direct drive in which the drive mechanism is more simple and so cheaper in construction.